Sujet: TROPICANA EMANUEL Kerry's keynote
Heure: 3 juin 2024 01:45 PM Paris
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https://zoom.us/j/93089760399?pwd=TnlEejFGTXVJdkRseGppZmtDL3FRdz09
ID de réunion: 930 8976 0399
Code secret: 045668
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ID de réunion: 930 8976 0399
Code secret: 045668
14H00 - 15H30 (Grand amphitheatre Institut Pascal Bat: 530 rue André Rivière Orsay 91400) :
A tropical cyclone is defined, somewhat tautologically, as “an intense circular storm that originates over warm tropical oceans and is characterized by low atmospheric pressure, high winds, and heavy rain,” to quote from the Encyclopedia Brittanica.
Yet under certain circumstances, cyclonic storms that strongly resemble tropical cyclones develop outside the tropics over waters whose temperature is below the canonical 26.5 C threshold used by most forecasters and researchers. Such storms, encompassing those that make up the title of this talk, have most of the distinctive features of tropical cyclones, including eyes, eyewalls, and spiral bands.
I will review what is known, observationally and theoretically, about such storms, and show that in most cases they form under synoptic-scale conditions in which the potential intensity and relative humidity are locally elevated above normal climatology by deep, cold lows aloft that have usually formed by Rossby wave breaking events. In some cases, such as Cyclone Daniel of 2023, the parent cold low can interact with the surface-based cyclone long after the latter has formed. I will argue that the observed structural differences between these storms and normal tropical cyclones can be attributed to the higher magnitude of the Coriolis parameter and the lower dry static stability along moist adiabats at lower temperatures. They appear to be part of the continuum between moist and dry surface flux-driven cyclones described by Cronin and Chavas.
